Method and apparatus for destacking sheet metal members

ABSTRACT

A device for separating flat objects such as sheet metal blanks has a pair of separator devices which apply a force to the edges of the objects at an angle to a normal of the plane of the objects. In one embodiment, the separator devices are screws which are rotated in opposite directions to lift opposite edges of the objects. As the object is lifted, the angle of the screws becomes more nearly vertical.

TECHNICAL FIELD

The present invention relates to a method of destacking, or separating,from one another sheet or panel-shaped, substantially planar objectssuch as sheet metal members which form a stack, the separation beingeffected in a separation direction which is substantially parallel witha normal to the plane of those objects which are to be separated and isexecuted by at least one separator device.

The present invention also relates to an apparatus for destacking, orseparating, sheet or panel-shaped, substantially planar objects such assheet metal members which form a stack, comprising at least oneseparator device such as a screw or the like which presents to the stacka number of engagement members which, seen from the stack, are movablein a feeding direction in order, by engagement with the stack, toseparate objects therefrom piecewise.

BACKGROUND ART

In the production of various products of sheet metal by pressing, use isoften made of sheet metal blanks which are piled into stacks in whichthe individual blanks lie directly on top of one another. The sheetmetal blanks often carry an oil film, which entails that they show amanifest tendency to adhere to one another. On removal of the sheetmetal blanks for further processing in a press or press line, use ismade of different forms of gripping devices which, for example, mayconsist of suction cups which are applied to the uppermost sheet in thestack and which lift the sheet from the stack and move the sheet intothe tool in the press.

If the sheets consist of magnetic material, the adhesive action of theoil film can be cancelled out by magnetic separators which prevent thesuction cups from taking two or more sheets at the same time, whichwould cause immediate operational stoppage in the pressing operation.

If the sheets consist of non-magnetic material, for example aluminium,the technique employing magnetic separation will not function, for whichreason adhesion between the sheet blanks implies almost constantoperational stoppage.

In other technical fields of application in which separation of membersor objects disposed in a stack has been brought into consideration, usehas been made of screw-shaped separator devices which, with theirthreads, grip in between adjacent objects and lift out the uppermostobject from the stack. In such instance, the axes of rotation of thescrews are parallel with the edge of the stack, i.e. also parallel witha normal to the plane of that object or member which is to be separated.

This technique, known from the packaging industry, functions well onlyin such contexts where those portions of the objects which are graspedby the screws are spaced apart from one another such that the screwthread can pass into these gaps without damaging the objects. On theother hand, it is impossible to apply this technique successfully insuch cases in which the objects or members form a compact stack which,thus displays no spacings between those portions of the objects whichserve for engagement for the screws.

Nor can the technique known from the packaging industry be employed insuch cases in which those objects which are to be separated do not liein well-arranged stacks, such that individual objects may project outlaterally beyond the rest of the stack. Precisely such poor precision inthe stacks, i.e. individual sheets or groups of sheets projectinglaterally out from the stack is difficult to avoid in the feeding ofsheets to, for example, a press.

Despite the above-outlined problems in compact stacks and employingscrews whose axes of rotation are parallel with the edge of the stack,Russian patent specification 870 322 discloses a solution which is basedon this principle. In the design and construction according to thisRussian patent publication, use is made of a screw whose thread has asharp knife edge which projects out along a radius and which is intendedto cut in between two adjacent sheets. Naturally, extremely strictrequirements on precision are placed here if such an apparatus is to becapable of separating from one another metal sheets of the order ofthickness of between 0,5 and 1,0 mm. Even one or a couple of tenths of amillimetre of incorrect placement of the cutting edge in relation to thestack will result in the sheets being damaged and deformed--with animminent risk of operational stoppage. There is a risk of exactly thesame outcome if the sheets in the stack suffer from edge damageresulting, for example, from impact. How great these precision problemscan be is most readily apparent from the fact that the sheets underconsideration here are a square metre or more in size and that the stackmay weigh several tonnes.

SUMMARY OF THE INVENTION

The present invention has for its object to realise a method of the typementioned by way of introduction, the method permitting a reliable andefficient separation of the metal sheets in a stack from one another sothat only one sheet member is grasped at a time. The present inventionfurther has for its object to realise a method which may be reduced intopractice using simple and versatile means so that variations in sheetmetal thickness and sheet dimensions--and also in the position of theindividual sheets--may thereby readily be managed.

The present invention yet further has for its object to devise anapparatus of the type mentioned by way of introduction, the apparatusbeing of such a nature that it affords an extremely operationallyreliable separation of the metal sheets from one another, that it issimple and economical to manufacture, and that it is versatile so thatit may readily be used for sheets of varying thickness and otherwisevarying dimensions and also for sheets whose position in the stack mayvary. In addition, the present invention relates to an apparatus whichaffords an accurate positioning of the destacked sheet metal member whenthis is to be grasped by a gripping device for infeed into a subsequentprocessing machine.

The objects forming the basis of the present invention will be attained,in respect of the method, if the method is characterized in that an edgeportion of the member or object which is to be separated is subjected,by the separator device, to a force which has a first component directedwith and substantially parallel with the separation direction, and asecond component substantially parallel with the plane of the objectwhich is to be separated and directed from the separator device intowards the object.

The objects forming the basis of the present invention will be attained,in respect of the apparatus, if the apparatus is characterized in thatthe feeding direction makes an angle with the normal to that objectwhich is to be separated; and that the separator device is in abutmentagainst the stack at one edge of that object which is to be separated.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will now be described in greater detailhereinbelow, with particular reference to the accompanying Drawings. Inthe accompanying Drawings:

FIG. 1 schematically illustrates a vertical front elevation of a firstembodiment of the present invention;

FIG. 2 is a top plan view of the embodiment of FIG. 1;

FIG. 3 is a perspective view of the embodiment according to FIGS. 1 and2;

FIG. 4 is a view corresponding to that of FIG. 1 of a second embodimentof the present invention;

FIG. 5 is a view corresponding to that of FIG. 1 of a third embodimentof the present invention;

FIG. 6 is a view corresponding to that of FIG. 1 of a fourth embodimentof the present invention;

FIG. 7 is a view corresponding to that of FIG. 1 of a fifth embodimentof the present invention; and

FIG. 8 is a view corresponding to that of FIG. 1 of a sixth embodimentof the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

In its most generic form, the apparatus according to the presentinvention comprises at least one separator device 1 in abutment againstan upper edge portion of that stack 2 of objects 3 which are to beseparated from one another so that adhesion between the objects causedby oil film or other agents may thereby be canceled and the uppermostobject in the stack can be grasped by a gripping device 4 for infeedinto a processing machine, for example a press. The separator device 1has at least one, possibly more, engagement members which, seen from thestack 2 in sequence after one another,move along a feeding direction 5away from the stack. The intended separation or partitioning direction 6is parallel with or substantially parallel with a normal to the plane ofextent of the objects 3.

The feeding direction 5 makes an angle with the separation direction 6and inclines inwardly and upwardly over the objects 3 and therebysubjects the objects to a force component substantially parallel withthe separation direction 6 and a force component approximately parallelwith the plane of extent of the objects 3, this second force componentbeing directed away from the separator device in towards the stack 2transversely of or substantially at right angles to that edge of theobject 3 against which the separator device abuts. The separator deviceengages with an upper corner edge portion of the stack 2, i.e. with anedge of the uppermost object 3, and the feeding direction 5 can make anangle with the separation direction 6 of the order of magnitude ofbetween 20°and 60°, preferably approx. 45°. This angle may vary during aseparation cycle and be reduced from a relatively large starting value(60°-40°) to a smaller final value (40°-20°). The angle may also beconstant.

FIG. 1 shows two opposing separator devices 1, but, according to thepresent invention, it is sufficient in certain cases with but a singleseparator device if the opposingly located edge of the stack 2 inrelation to the separator device is supported by a fixed arrest whichprevents displacement of the objects 3 in this direction, i.e. in adirection away from the separator device.

In the alternative with the single separator device and an arrest, theseparator device will, in the normal case, enter into engagement withthe upper edge portion of the uppermost object 3 in the stack. Thisupper edge portion is subjected to a force, on the one hand, in theseparation direction 6 and, on the other hand, in the plane of extent ofthe object so that this tends to be lifted and displaced into abutmentagainst the arrest if such abutment does not already exist beforehand.As soon as the uppermost object has been stopped by the arrest, its edgein engagement with the separator device will be separated from thesubjacent stack and be lifted away therefrom so that the adhesive actionof the oil film is broken.

In order to permit the above-described movement, it is necessary thatthe separator device 1 can be pivoted away from the stack 2 to someextent or be displaced away from it in order thereby to avoid bendingand deforming of the object 3.

If, for example, the next uppermost sheet in a stack 2 were to projectout beyond the stack in a direction towards the separator device, theseparator device will first come into engagement with this sheet. Insuch an event, the sheet will, on the one hand, be lifted from the stackin the separation direction 6 but will also be displaced in the plane ofextent of the sheet as soon as the adhesive action of the oil film hasbeen reduced or cancelled. In such instance, the sheet will be slid intocontact against the arrest member, in which event the separator devicewill instead enter into engagement with the uppermost sheet in thestack, since the separator device inclines in a direction in over thestack. Thereafter, separation of the uppermost sheet continues in themanner described in the foregoing.

In the alternative with two opposing separator devices 1, engagementwill be established in the normal case (no sheet projecting outlaterally to any appreciable degree) approximately simultaneouslybetween the separator devices 1 and opposing edges of the uppermostsheet 3, whereafter the opposing edges of the sheet are raised so thatadhesion with the subjacent sheet is broken.

In such an alternative in which, for example, the next uppermost sheetprojects out laterally, this will be grasped by the separator devicelocated there. Approximately at the same time, the uppermost sheet willbe grasped by the other separator device. As soon as the projectingsheet has been lifted by its separator device from the stack, it will bedisplaced laterally in under the uppermost sheet, for which reasonengagement will be moved up to this sheet which is then lifted from thesubjacent sheet.

In the embodiment illustrated in FIGS. 1-3, use is made of two opposingseparator devices 1 in the form of threaded worms or screws 12 whichabut against the upper opposing corner edges of the stack 2. For reasonswhich will be elaborated upon below, the screws 12 are disposed forcounter-rotation and, therefore, their threads are also of oppositeturn.

The screws each have their drive unit 7 which comprises a gear 8 and amotor 9. The drive unit 7 is suspended in a bracket 10 which is pivotalabout a shaft 11 so that thereby the screws may execute pivoting motionsand thereby be distanced from one another according as an object 3 isled up along the screws. This pivoting entails that the angle betweenthe separation direction 6 and the feeding direction 5 will graduallydecrease as the separation and pivoting of the screws 12 continues.

The pivot shaft 11 is placed in such a manner in relation to the centreof gravity of the bracket 10, the drive unit 7 and the screw 12 that thescrews strive to be pivoted in towards the stack 2 and abut against thestack. As a result, the screws will be pretensioned in a direction intowards the stack.

It will be apparent from FIG. 3 that the drive units 7 are secured viathe shafts 11 to abutments 13 which are located closely adjacent theside edges 22 of the stack 2 against which the screws 12 abut. It willalso be apparent that these abutments 13 are of such height as to extendup over the uppermost sheet 3 in the stack 2.

In order to function satisfactorily, the pitch of the screws 12 mustapproximate or preferably exceed the sheet thickness. At the same time,there is hardly any upper limit to the distance between two mutuallysubsequent engagement members or threads, but, for practical reasons,this distance should not substantially exceed twice the sheet thickness.Given that the subject matter of the present invention is intended to beusable in connection with varying thicknesses, it will be readilyperceived that the screws 12 must be replaceably secured in the driveunits 7, preferably the gears 8.

Practical experiments have demonstrated that the function of theapparatus will be satisfactory if the pitch of the screws 12 lies in therange of between 1.2 and 1.8 times the relevant sheet thickness.However, the pitch should preferably be about 1.5 times the sheetthickness and the thread profile should be symmetrical (ISO profile)with a slightly rounded thread crest, at least if the material in thesheets is soft, as is the case with aluminium.

It will be apparent from FIG. 3 that the pivoting of the drive units intowards the stack 2 may be governed with the aid of an adjustment screw14 which is disposed on a foundation portion of the drive unit. In orderto ensure satisfactory function while in operation, this adjustmentscrew should, however, not abut against the bracket but servesubstantially so as to prevent exaggerated pivoting of the drive unit ifthe sheet stack were to be completely emptied.

It was mentioned above that the pivot shaft 11 is located such that thepoint of gravity realises a suitable pretensioning force between thescrews 12 and the sheet stack 2. Naturally, such pretensioning may alsobe achieved by other forms of pretensioning devices, for examplesprings, pneumatic or hydraulic cylinders and the like.

It was also mentioned above that the screws 12 should becounter-rotating, and be of opposite turn. In such instance, thedirections of rotation should lie as shown in the Figure at the arrows15. The reason for this is that those friction forces which occurbetween the screw periphery and the uppermost sheet 3 give a third forcecomponent against the sheet, this force component being located in theplane of extent of the sheet and being directed as shown by the arrow16. When, thus, the uppermost sheet becomes free from the subjacentstack, the screws 12 strive to displace the sheet in the direction ofthe arrow 16. In order to prevent such displacement, use is made of anabutment 17 (FIG. 2) which guarantees accurate positioning of theuppermost sheet when this is to be grasped by the gripping device 4which preferably is provided with suction cups 18.

By using the opposing abutments 13, it will be ensured that the sheet islocated within the tolerance range which is indicated by the sizedifference between the sheet and the distance between the abutments 13.The striving on the part of the screws 12 to displace the sheet in adirection according to the arrow 16 towards the the abutment 17 furtherentails that the position of the sheet is very well defined also in thisdirection, for which reason the gripping devices 4 can deliver a sheetto a processing machine with a high level of precision.

As operation of the apparatus according to FIGS. 1 to 3 continues, theheight of the stack 2 will be reduced. This would entail that the driveunits 7 were pivoted more and more towards one another in over the stack2. In order to keep the angle between the intended separation direction6 and the feeding directions 5 of the separator device 1 withinpermitted limits, either the stack 2 is raised by degrees as operationcontinues, or the drive units 7 and the screws 12 are lowered togetherwith the abutments 13.

In order not to need modifying the range of movement of the grippingdevice 4, the alternative employing raising of the stack 2 is to bepreferred so that thereby the upper face of the stack will constantly beat approximately the same level.

DESCRIPTION OF ALTERNATIVE EMBODIMENTS

FIG. 4 shows one alternative embodiment in which the two above-disclosedscrews have been replaced by one or more, preferably two rotary bodies19. On their circumferential surface, the rotary bodies have a thread 20which is analogous with the thread of the screws 12.

The configuration of the rotary bodies 19 may generally be described asa solid of revolution in which the axis of rotation 21 may be verticaland parallel with the side edge 22 of the stack. Depending upon thedesign of the solid of revolution, the axis of rotation 21 may, however,also slope more or less in the same manner as the axis of rotation ofthe screws 12, but also in the opposite direction.

The generatrix of the solid of revolution 19 may be a straight line, inwhich event the solid of revolution is in the form of a truncated orwhole cone. However, the generatrix may also be an outwardly convexcurve. In the alternative with a straight generatrix, the feedingdirection 5 will be constant throughout the entire height of the solidof revolution. If, on the other hand, the generatrix is a curved line,the feeding direction 5 will vary along the height of the solid ofrevolution and, with the curve bent in the abovedescribed manner, theangle between the feeding direction 5 and the separation direction 6will decrease when the uppermost sheet 3 is transported upwards. Inorder to achieve this angular modification, the direction of the axis ofrotation 21 may also be modified.

In order to prevent the two solids of revolution from crushing orpowerfully deforming the sheet which is in motion upwards between them,the solids of revolution are movable in the horizontal plane towards andaway from one another and are pretensioned at suitable force in adirection in towards the stack 2. This entails that, when the uppermostsheet migrates upwards, the distance between the axes of rotation 21will increase in order rapidly once again to decrease when the uppermostsheet has arrived on the upper side of the solids of revolution or hasbeen removed by the gripping device 4 so that thereby the threads 20once again come into engagement with the stack.

As an alternative to the movement in the horizontal plane of the solidsof revolution 19, the direction of their axes of rotation 21 may bemodified so that the solids of revolution are inclined or pivotedoutwards from one another when the sheet 3 migrates upwards.

Also in this embodiment, rotation of the solids of revolution 19 takesplace in opposite directions as shown by means of the arrows 15. Also inthis embodiment, use is suitably made of an abutment 17 for positioningthe upper, destacked sheet 3.

In the embodiment according to FIG. 5, the separator devices consist ofone or more, preferably two wheels 23 or rotary disks which, with theirperiphery 24, abut against upper, preferably opposing edges of the stack2. The wheels 23 carry a peripheral coating which gives a high frictionin relation to the sheets 3 included in the stack, or also a groovedsurface in which the distance between adjacent grooves corresponds tothat described above for the threads of the screws 12. Furthermore, thelongitudinal direction of the grooves is parallel with the edges of thesheets 3 included in the stack 2.

The wheels 23 rotate in opposite directions, which is intimated by thearrows 25. This entails that the feeding directions 5 will lie along thetangents of the wheels in the point of contact with that sheet which isto be destacked and separated. According as the sheet migrates upwards,the feeding directions will make a steadily decreasing angle with theseparation direction 6 if the wheels are placed at a constant heightabove the stack 2. Also in this embodiment, it is necessary that thewheels 23 can move away from one another during a separation cycle,which may be achieved in that the journals of the wheels are movablehorizontally (approximately in the plane of extent of the uppermostsheet 3). Alternatively, the journals of the wheels 23 may be suspendedin pendulum arms so that the wheels may thereby be pivoted away inpendulum motion.

In this embodiment, the abutment 17 may be dispensed with, since thewheels 23 give no force component corresponding to the force componentin the direction 16 in FIG. 2.

In the embodiment according to FIG. 6, the separator devices 1 consistof one or more, preferably two endless circulating belts 26. The beltsrun over rotary rollers or rolls 27 which rotate in accordance with thearrows 28 in opposite directions. Hereby, the belts 26 will have feedingdirections 5 which correspond to the direction of those belt parts whichabut against the stack. In the same manner as that which applied to theperiphery of the wheels 23 in the embodiment according to FIG. 5, thebelts 26 have grooves or friction-increasing coatings on their facesengaging with the stack, this transferring the force to the sheets.

Nor in this embodiment is there any need for a counterpart to theabutment 17, since the belts 26 do not give a force component in theplane of extent of the sheets along the direction 16 illustrated in FIG.2.

In this embodiment, the angle between the feeding direction 5 and theintended separation direction 6 may be reduced during a separation cyclein that the assembly of belt/rollers is pivoted about the rotation axisof the lower roller 27 included in each assembly. Possibly, it is alsoconceivable that the assemblies are displaced in a horizontal directionaway from one another in order to make requisite room for the destackedand separated sheet.

In the embodiment according to FIG. 7, the separator devices 1 consistof one or more, preferably two endless, circulating belts 29 which aresupported and which turn about or between rollers 30. The rollers 30 ineach separator device 1 have axes of rotation 31 which are parallel withone another and which are also parallel with the feeding directions 5 ofthe separator devices.

In order to achieve the sought-for destacking and separation of thesheets 3, the belts 29 are provided, on their outer faces abuttingagainst the stack 2, with a grooving 32 in which the direction of thegrooving is such that that part of the grooving which is "passed about"the roller 30 located in abutment with the stack 2 will form a thread onthe surface of the roller the grooving 32 thus has an angle of pitch inrelation to a diameter plane to the rotating rollers 30. The distancebetween adjacent grooves corresponds to that disclosed for the thread ofthe screws 12 in the embodiment according to FIGS. 1-3.

Also in this embodiment, the roller belts of the assembly must bemovable in analogy with that described above.

In the embodiment according to FIG. 8, the separator devices 1 consistof one or more, preferably two feeder devices 33 which are elongate andlinearly reciprocal in accordance with the arrows 34. The feeder devices33 are provided, on their sides facing the stack 2, with a transverselydirected groove (parallel with the upper edge line of the stack), thedistance between adjacent grooves corresponding to that mentioned abovefor the thread of the screws 12.

Superposed on the reciprocal movement according to the arrow 34 of thefeeder device 33, there is also a pendulum pivotal motion, which impliesthat the upper ends of the feeder devices can be brought to a greaterdistance from one another so that thereby requisite room will be createdfor the sheet 3 being fed.

Further modifications are conceivable without departing from the spiritand scope of the appended claims.

We claim:
 1. An apparatus for destacking, or separating, sheet orpanel-shaped, substantially planar objects such as sheet metal memberswhich form a stack, comprising at least one separator device engagingthe stack and presenting to the stack a number of engagement memberswhich, seen from the stack, are movable in a feeding direction formingart angle with a normal to the plane of the object to be separated andapparatus for turning the separator device to apply a force in thefeeding direction, the separator device, with a portion engaging thestack, movable towards and away from the stack and yieldably biasedagainst an edge portion of an object to be separated.
 2. The apparatusas claimed in claim 1, characterized by two separator devices disposedat opposing edges of the stack and whose feeding directions makesubstantially equal but counter-directed angles with a normal to theplane of that object to be separated.
 3. The apparatus as claimed inclaim 2, characterized in that the separator devices are substantiallycylindrical screws.
 4. The apparatus as claimed in claim 3,characterized in that the screws are driven in opposite directions,whereby the object to be separated is subjected to a force approximatelyin the plane of the object; and that an abutment is provided so as toinhibit displacement of the object to be separated in the direction ofthe abutment.
 5. The apparatus as claimed in claim 3, characterized inthat the screws are provided with drive means pivotally disposed aboutshafts extending substantially parallel with edges of the stack engagedby the screws; and that the shafts are disposed such a distance from thestack that the screws are pivoted by force of gravity to positions wherethe screws engage the stack.
 6. The apparatus as claimed in claim 2,characterized in that the separator devices are displaceable such thatportions of the two separator devices engaging the object to beseparated are movable towards and away from one another.
 7. Theapparatus as claimed in claim 1, characterized in that the distancebetween two adjacent engagement members seen from the stack is greaterthan the thickness of the object to be separated, preferably in therange of between 1.2 times said thickness and 1.8 times said thickness.8. The apparatus as claimed in claim 7, characterized in that saiddistance is approximately 1.5 times said thickness.
 9. The apparatus asclaimed in claim 1, characterized in that the at least one separatordevice is replaceable for adaptation to the thickness of an object to beseparated.
 10. The apparatus as claimed in claim 1, characterized inthat the separator device and the stack are adjustable in the verticaldirection in relation to one another for adaptation of the relativeheight position as the stack is consumed.
 11. The apparatus as claimedin claim 1, characterized in that the at least one separator device is aconical solid of revolution, having a circumferential surface providedwith a thread in engagement with the object to be separated; and thatthe direction of a tangent to the solid of revolution in its region ofengagement with the object substantially corresponding to the feedingdirection.
 12. The apparatus as claimed in claim 1, characterized inthat the at least one separator device is a wheel having periphery inengagement with the object to be separated, the direction of a tangentto the wheel in the region of contact with the object substantiallycorresponding to the feeding direction and the wheel being rotary abouta shaft which is approximately parallel with an edge of the objectengaged by the wheel.
 13. The apparatus as claimed in claim 1,characterized in that the at least one separator device comprises agrooved device movably disposed at least in their longitudinaldirection, and having a direction of movement during one separationcycle substantially corresponding to the feeding direction.
 14. Anapparatus for destacking, or separating, sheet or panel-shaped,substantially planar objects such as sheet metal members which form astack comprising:at least one separator device comprising an endless,circulating belt in engagement with an edge of the object to beseparated, the direction of circulation of the belt in the region ofcontact with the object to be separated substantially corresponding to afeeding direction forming an angle with a normal to the plane of theobject to be separated; and rollers for carrying the belt about a shaftwhich extends approximately parallel to the edge of the object engagedby the belt; the separator device movable toward and away from the stackand yieldably biased against an edge portion of an object to beseparated.
 15. An apparatus for destacking, or separating, sheet orpanel-shaped, substantially planar objects such as sheet metal memberswhich form a stack, comprising:at least one separator device comprisingan endless, circulating belt in engagement with an edge of the object tobe separated, the belt being disposed about two rollers, each having ashaft extending parallel to a feeding direction forming an angle with anormal to the plane of the object to be separated, the belt having agroove which has a pitch in relation to the diameter plane of each ofthe rollers; the separator device movable toward and away from the stackand yiedably biased against an edge portion of an object to beseparated.
 16. A method of destacking a plurality of substantiallyplanar objects such as sheet metal members each extending in a plane andforming a stack, the method comprising the steps of:applying to an edgeof an object to be separated a separating force to move an object to beseparated in a direction of separation which is substantially normal tothe plane of the object to separated by yieldably pressing a separatordevice against an edge portion of the object to be separated and turningthe separator device; the separator device presenting a plurality ofengagement members to the stack operative to apply a separating force toan edge of an object to be separated in a direction forming an acuteangle with the direction of separation.
 17. The method in accordancewith claim 16 wherein the step of applying a separating force comprisesapplying a force having a first component extending in a directionsubstantially parallel to the direction of separation and a second forcecomponent directed inwardly towards the object and substantiallyparallel to the plane of the object to be separated, the method furthercomprising the step of reducing the angle between the first and secondforce components as the object to be separated is moved in the directionof separation.
 18. The method in accordance with claim 17 comprisesdisplacing the object to be separated substantially in the predeterminedplane by application of the second force component and into contact withan additional separation device and applying an additional force havinga first force component extending substantially in the direction ofseparation and a second force component extending toward the object tobe separated and in a direction which is substantially parallel to theplane of the object to be separated.
 19. The method in accordance withclaim 18 wherein the separating force and the additional force eachcomprise a third force component applied to the object to be separated,the third force components extending substantially parallel with oneanother and the plane of the object to be separated.